The epidemic of Acquired Immune Deficiency Syndrome (AIDS) has greatly intensified the concern among the medical community of the accidental infection of health care workers by contaminated body fluids. Of course the problem existed prior to the spread of AIDS because of the risk of contracting hepatitis viruses, venereal diseases, and other infectious agents from such things as accidental needle stick injuries. Nevertheless, the fatality rate with AIDS and uncertainty, at least in the early years, of the means of infection and probability of contracting the disease upon exposure to contaminated body fluids has given rise to a virtual explosion of inventive activity directed to minimizing the risks to health care workers occupationally exposed to those being treated for AIDS or which may carry, without their own knowledge, the Human Immunodeficiency Virus (HIV) which causes AIDS.
The problem is not only the relatively modest statistical risk of a health care worker contracting AIDS or AIDS-Related Complex. It is also the economic cost of repeated testing of and psychological impact to the many health care workers who are directly exposed to contaminated body fluids through various relatively common accidents that occur in health care facilities notwithstanding the increased attention paid by exposed personnel. In addition to the inventive activity above described, there have been a number of published studies investigating the nature of accidents whereby health care workers are exposed to contaminated body fluids. These have determined that the overwhelming majority of such injuries are caused by accidental needle sticks or other sharp object injuries, but there are also included mucous membrane splashes and contamination of open wounds. There is, for example, one instance where there was minimal cutaneous blood exposure to a health care worker had chapped hands at the time of contact and thereafter contracted the HIV. In one study published by Jagger in The New England Journal of Medicine on Aug. 4, 1988, entitled Rates of Needle-Stick Injury Caused By Various Devices in a University Hospital, it was determined that disposable syringes accounted for thirty-five (35%) percent of needle stick injuries, prefilled cartridge syringes for twelve (12%) percent, winged steel-needle sets for seven (7%) percent, phlebotomy needles for five (5%) percent and intravenous catheter stylets for two (2%) percent, with all other devices accounting for thirteen (13%) percent.
Much of the inventive activity appears to be directed toward development of syringes which can be recapped or otherwise protected following contamination without any movement of the health care worker's hand in the direction of the point of the needle. Of course, there was substantial prior art where that particular criterion was not a factor, some of which appears to have predated the concern caused by the AIDS epidemic.
Some of the criteria that bear on the question of the practical value of any modification of prior art health care practices follow. These include a simple and inexpensive device with uncomplicated usage, extremely low manufacturing and selling costs, a design which minimizes the need for the retraining of health care workers, little or no user assembly, fast and convenient use, the absence of a need to cover the needle using a motion that passes the user's hand toward the point of the needle, a device that does not require the health care worker to be exposed to hazardous conduct in employing same, and a safety feature that remains in effect after disposal thereby protecting trash handlers.
The prior art includes a number of interesting references. Several were directed to shielding of syringes for radioactivity, i.e., those directed to protection of health care workers, exposure to radioactive medications, or agents contained in a syringe. The first of these was Collica, et al., U.S. Pat. No. 4,060,073, which included a slot for transparent radiation shielding for a transparent radiation shielding window so that the health care worker can observe the location of the syringe plunger.
Another reference teaching a protective shielding assembly for use with a syringe incorporating radioactive material is Larrabee, U.S. Pat. No. 3,993,063. This reference teaches radioactive shielding in the form of a container in which is disposed a vial of radioactive medication or other material and a syringe, each disposed in a portion which is slidable with respect to the other so as to permit the needle of the syringe to penetrate the septum of the vial for withdrawing into the syringe the medication or other material.
A further reference is U.S. Pat. No. 4,564,054 issued to Gustavsson for a fluid transfer system which includes accordion sidewalls and several membranes for the purpose of preventing air contamination when transferring a substance from one vessel to another, the latter frequently a syringe. The accordion sidewall construction is a substitute for the slidable portions of the preceding reference, even though the purposes of the two are dissimilar. The latter reference includes numerous embodiments, however, none of them teach or suggest the present invention.
One of the references that predates the AIDS epidemic is a device and technique for minimizing risk of contamination by a blood sample patented by Bordow, U.S. Pat. No. 4,085,737, which includes a cap for a syringe needle with a vacuum chamber to purge air and some blood. This reference is ineffective to protect against needle sticks because it actually requires movement of the cap toward the needle and some force to be applied to cause penetration of a fluid impervious seal disposed interiorly of the device.
As indicated above, a number of references have been patented in response to the AIDS epidemic and crisis among health care workers and attempt to protect the latter from accidental needle stick injuries. One of these is Luther, U.S. Pat. No. 4,747,836, which teaches a needle guard and assembly having a sleeve which rotates in a spiral slot to extend over the needle. When opened, the guard pivots out of the way.
Another reference of some interest is the patent issued to Spencer for a sheathed syringe, U.S. Pat. No. 4,723,943, which teaches a slidable sleeve disposed about the syringe and which can be extended by motion away from the point of the needle to protect against accidental needle sticks. The sheath is rotated in one direction for temporary extension and is rotated in another direction for extension that is locking and prevents further retraction. The device allows either re-use or protection for disposal but requires alignment and particular care of the health care worker in its use. Spencer also suffers from the expensive limitation that one such device is needed for each syringe, and requires different dimensions for each different size syringe.
A similar inventive purpose is apparent in the invention of Masters, et al. for a syringe with a safety sheath, U.S. Pat. No. 4,681,567. It teaches a slidable sheath which locks into position when extended and can also be operated without motion of a health care worker's hand toward the point of the syringe needle.
Another reference is the invention of Alvarez for a retractable syringe needle cover that has a locking means, U.S. Pat. No. 4,139,009. Alvarez teaches a plurality of elastically resilient arms surrounding the syringe needle attached to an annular slide member which surrounds the needle and slides with respect to said needle by flexure of the resilient arms. Locking is achieved by movement of a slidable locking ring about the central portion of the resilient arms. One additional reference is the McDonald Safe Guard Needle described in a medical technology article on pp. 120,21 of the Oct. 23, 1989 issue of Design News. This invention utilizes a shield tube that automatically extends when the needle is pulled from a catheter, with which the device is intended for use.